Leon is a French smasher who plays both Melee and Brawl. As he chose his nickname shortly after Brawl was released, most Melee players still know him as Nassim, his real name.

He surprised many players at Epita Smash Arena, his first tournament. While he was not aware of advanced techniques at the time, he had developed his own playstyle and combos with Roy, and managed to reach a decent place.

He originally mained Peach in Brawl, and was often referred as the French Brawl Champion, since he placed first in most of the Brawl tournaments in France in 2008 (and thus placed 1st in the 2008 Rankings) with her. Counting tournaments in anime conventions, Leon won 9 tournaments in 2008, 7 in a row, 3 being Bushido Impact events.

He is now primarily a Marth player, and continues to place high in tournaments that he enters, though his extremely aggressive playstyle occasionally works to his detriment, as seen here.

Leon frequently attended major tournaments in North America, such as SKTAR and the Apex tournament series, where he has achieved significant placings. He has taken sets off of top players such as DEHF. He moved to Ontario after Apex 2014, but moved back to France after 5 months. Leon was ranked at the 0 position on the BrawlSouthern Ontario Power Rankings.

He was formerly a member of the Bushido Impact staff starting in July 2009.

He still plays Project M, and is currently ranked 3rd on the French Project M Power Rankings.